Steam generated in fossil fuel-fueled boilers is widely used in industry, especially in electrical power generation, and in oil fields to generate steam where secondary and tertiary recovery of oil is conducted. These are high-temperature boilers with substantial capacities, usually using liquid fuel oil or natural gas, and the quantity of pollutants produced by them is considerable. Oxides of nitrogen, which are generated primarily in the combustion flame, are of particular concern. In fact, the matter is so serious that if the pollution rate is not reduced, further increases in production of heavy oil, which is dependent on heat are threatened, because to generate so much additional heat with existing combustion processes threatens to increase the total atmospheric pollution to unacceptable levels.
It is an object of this invention to provide a simple method for reducing the level of oxides of nitrogen which are generated in the flame combustion of carbonaceous fuels.
It is another object of the invention to improve the efficiency of a boiler by enabling its burner to operate with close-to-stoichiometric mixtures, thereby enabling the effluent gases to remain longer in the heat exchanger as a consequence of the reduced flow of gas per unit of fuel that is burned.